Patent Literature 1 describes an example of a conventional seat reclining device for use in a vehicle. This vehicle seat reclining device includes a fixed disk (11), which has guide grooves (11c), a movable disk (12), which has internal teeth and which is axially supported on the fixed disk, a plurality of poles (15A to 15D), cam bodies (16, 18), and an unlock member (19). The guide grooves guide the corresponding poles (15A to 15D) in the radial direction. Each pole (15A to 15D) has external teeth (15b), which can be engaged with and disengaged from the internal teeth, a cam pin (15e), which extends from the pole, and a locking-side pole cam portion (15f), which is formed on an inner circumferential side of the pole. The cam bodies (16 and 18) press the poles outwardly as they rotate in one direction to engage the internal teeth with the external teeth. The cam bodies (16 and 18) pull the poles inwardly as they rotate in the other direction to disengage the internal teeth from the external teeth. The unlock member (19) is coupled to the movable disk (12) and integrally rotated with the disc. The unlock member (19) is engaged with the first pole (15A) of the four poles when the relative angles of rotation of the fixed disk and the movable disk are within a predetermined range (hereafter, this range is referred to as an unlocking section). This prohibits engagement of the internal teeth and the external teeth. The rotation restriction of the cam bodies prohibits engagement of the internal teeth and the external teeth in the three second poles (15B to 15D) among the four poles.
More specifically, each cam body includes a cam (16) and a release plate (18), which are coupled together so as to rotate integrally. The cam (16) includes a plurality of locking-side cam portions (16b to 16d), which are formed on the outer circumference of the cam. The release plate (18) includes an unlocking-side cam portion (18d), which forms an elongated hole. The locking-side cam portions (16b to 16d) of the cam body press the locking-side pole cam (15f) as the cam body rotates in one direction and engages the internal teeth with the external teeth. This restricts relative rotation of the fixed disk and the movable disk, and restricts rotation of the seat back relative to the seat cushion.
The unlocking-side cam portion (18d) of the cam body pulls the cam pin (15e) as the cam body rotates in the other direction. This disengages the internal teeth from the external teeth. As a result, relative rotation of the fixed disk and the movable disk is permitted, and rotation of the seat back relative to the seat cushion is permitted.
The above structure allows the seat back to be adjusted and retained at a predetermined angle of inclination that is optimum for a passenger seating.
The unlock member includes a restriction unit (19c), which extends in the circumferential direction. The restriction unit forms an elongated hole including steps. The restriction unit includes a wide-hole part (19c1) and a narrow-hole part (19c2), which have different opening widths in the radial direction. When the relative rotation angles of the fixed disk and the movable disk are within a locking section that is outside the unlocking section, the wide-hole part is set on the cam pin of the first pole. The cam pin is permitted to move in the radially outward direction without interfering with the wide-hole part. This allows the external teeth of the first pole to be engaged with the internal teeth. At the same time, by permitting rotation of the cam and the release plate of each second pole, engagement of the external teeth of the second pole with the internal teeth is permitted.
The restriction unit is set in a manner that the narrow-hole part is arranged on the cam pin of the first pole when the relative rotation angles of the fixed disk and the movable disk are within the unlocking section. The cam pin of the first pole comes in contact with and interferes with the narrow-hole part to restrict the movement of the cam pin in the radially outward direction. This prohibits engagement of the external teeth of the first pole with the internal teeth. At the same time, by restricting the rotation of the cam and the release plate, the external teeth of each of the three second poles with the internal teeth is prohibited. More specifically, each second pole is engaged with the release plate, of which rotation is restricted, to avoid contact of the external teeth of each second pole with the internal teeth. As described above, a specific pole (first pole) can be solely engaged with the unlock member to prohibit engagement of the external teeth of the specific pole (first pole) with the internal teeth, as well as prohibit engagement of, through the release plate, the external teeth of each of the other poles (second poles) with the internal teeth. If, for example, all the poles are equally engaged with the unlock member to prohibit engagement of the external teeth of each pole with the internal teeth, the unlocking section would be enlarged and the range of angles at which the seat back can be arranged would be narrowed.
Patent Literature 1: Japanese Patent No. 3804431